Decline in the Index of Biotic Integrity of the Fish Assemblage as a Response to Reservoir Aging

Abstract

The fish assemblage from reservoir Medjuvrsje was monitored over the 1955-2000 period. The Medjuvrsje Reservoir is one of the oldest Serbian reservoirs formed in 1953. Ichthyofauna was sampled in 1955, 1984, 1991 and 2000. Modified index of biotic integrity (IBI) metrics were used to assess changes in biotic integrity. The relative abundance of omnivorous, phytophilic and tolerant species increased, that of lithophilic, intolerant and rheophilic species decreasing during the 45 years. The total IBI decreased from 44 in 1955 to 24 in 2000, while the sediment deposition rate increased from 26.8% in 1963 to 70.4% in 2005. There was a significant negative correlation between the IBI and the sediment deposition rate. This study showed that the IBI could be used to characterize the status of the reservoir.